gralloc: update doc to reflect security change
The MetadataType must be prepended to any StandardMetadataType byte
stream. The encode/decode support library already adds the MetadataType.
This patch updates the documentation.
Test: Compiles
Bug: 137966819
Change-Id: I620f3cc0edd088b062844bb7a718f34360454d71
diff --git a/graphics/common/aidl/android/hardware/graphics/common/StandardMetadataType.aidl b/graphics/common/aidl/android/hardware/graphics/common/StandardMetadataType.aidl
index 060d12c..e5a189e 100644
--- a/graphics/common/aidl/android/hardware/graphics/common/StandardMetadataType.aidl
+++ b/graphics/common/aidl/android/hardware/graphics/common/StandardMetadataType.aidl
@@ -24,6 +24,15 @@
*
* [email protected] must support getting the following standard buffer metadata types. [email protected] may
* support setting these standard buffer metadata types as well.
+ *
+ * When encoding these StandardMetadataTypes into a byte stream, the associated MetadataType is
+ * is first encoded followed by the StandardMetadataType value. The MetadataType is encoded by
+ * writing the length of MetadataType.name using 8 bytes in little endian, followed by a char
+ * array of MetadataType.name's characters. The char array is not null terminated. Finally,
+ * MetadataType.value is represented by 8 bytes written in little endian.
+ *
+ * The StandardMetadataType encode/decode support library can be found in:
+ * frameworks/native/libs/gralloc/types/include/gralloctypes/Gralloc4.h.
*/
@VintfStability
@Backing(type="long")
